A note on tone: this guide keeps the jokes to a minimum, on purpose. Everything else on this site is about getting sharper pictures. This one is about keeping your eyesight.
Telescopes and camera lenses gather and concentrate light. Point one at the Sun without proper protection, and it can permanently damage your eyes in an instant, destroy your camera's sensor, and even start a fire. Every rule below exists because someone learned it the hard way.
The rules
- Always use a full-aperture filter on the front of your telescope or lens. The filter must cover the entire front opening, so sunlight is filtered before it enters the optics.
- Never use a filter that goes behind the optics. Some old telescope kits came with "sun filters" that screw into the eyepiece. Throw them away. Sunlight is already concentrated at that point, and those filters can crack without warning.
- Eclipse glasses are for your eyes only, not your gear. Certified eclipse glasses (ISO 12312-2) are safe for looking at the Sun with your naked eyes. They are not safe to look through a telescope, binoculars, or camera viewfinder, even when you're wearing them. The concentrated light can burn right through.
- Inspect your filter before every session. Hold it up to a bright lamp. If you see any pinholes of light, tears, scratches, or creases, do not use it.
- Make sure it can't fall or blow off. Secure the filter firmly before you look. A gust of wind should not be able to remove it.
- Cap or remove your finder scope. A finder scope is a small telescope. Unfiltered, it's just as dangerous as the main one, and it's easy to forget.
- Never remove the filter while pointed at the Sun. Point away first.
- Supervise children at all times. Curiosity plus an unattended telescope is a dangerous combination.
Cameras: live view vs. viewfinder
With a proper front-mounted solar filter in place, you can photograph the Sun safely. Without one, an optical viewfinder sends concentrated sunlight straight into your eye, and live view can damage your sensor. Filter first, always.
How to focus on the Sun
Here's something that surprises people: a Bahtinov mask doesn't work on the Sun. It needs a point of light, like a star, and the Sun is a disk. Instead:
- With your solar filter on, focus on the sharp edge of the Sun's disk, or on a sunspot if one is visible.
- Or pre-focus the night before on a bright star using your Bahtinov mask, then tape your focus ring. Focus can shift slightly with temperature between night and day, so do a final check on the Sun's edge.
Solar eclipses
Keep your filter on through every partial phase, from the first bite out of the Sun to the very last. Only during the brief moment of totality in a total eclipse is it safe to look without a filter, and the filter must be back on before the first sliver of Sun reappears. If you're not experienced with this, simply leave the filter on the whole time. The next total solar eclipse visible from the United States is on August 23, 2044.
Gear for safe solar viewing
- Adjustable Telescope Solar Filter: front-mounted, genuine Baader AstroSolar film, fits outside diameters from 86 to 117 mm.
- ISO 12312-2 Solar Eclipse Glasses: for naked-eye viewing only.
For exposure settings and shooting technique, see our blog post on photographing the Sun.